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Botswana International University of Science & Technology (BIUST) 2021

Surface water demand and supply of Gaborone city and surrounding areas under climate change and population growth

Mphoeng, Bosa

Titre : Surface water demand and supply of Gaborone city and surrounding areas under climate change and population growth

Auteur : Mphoeng, Bosa

Université de soutenance : Botswana International University of Science & Technology (BIUST)

Grade MSc Environmental Science 2021

Résumé partiel
The adequate supply of the ever-increasing demand of fresh water continues to be a global challenge due to increase in population. The anticipation for better lifestyles and improved water supply has resulted in an increase in migration from rural settlements leading to an increase in the populations of many cities globally. This study therefore investigates the variability and trends in the surface water demand and supply of the city of Gaborone and surrounding areas in response to anticipated population growth and climate change using the Water Evaluation and Planning (WEAP) model for future periods. The model was run with the current accounts and reference period set at 2014 and 2015-2100 respectively to predict their possible impacts on the water balance and allocation of the region due to varied water demands. Moreover, the study includes analysis of population trends, water production and consumption rates, hydrological information as well as projected rainfall over the catchment supplying water to Gaborone Dam. The rainfall data over the catchment, simulated in the frame work of Coupled Model Intercomparison Project Phase 5 (CMIP5) by Max Planck Institute Earth System Model Mixed Resolution (MPI-ESM-MR) for scenario periods, are statistically downscaled using the high resolution Worldclim data to spatial resolution of 1 km2 and bias corrected against Global Climatology Precipitation Center (GPCC) precipitation. The downscaled rainfall data are then employed in WEAP model and climate trend analysis. The stream flow of Notwane River has decreased from 0.65 MCM in 2006 to 0.53 MCM in 2016. The change is consistent with decrease in rainfall in the area. The WEAP simulated flow of Notwane River station with the observed flow gives an EF (Coefficient of Efficiency) of 0.91 which is a good correlation. The analysis shows that the projected population of Gaborone, Mogoditshane and Tlokweng using the high population growth rate of 3.4% will be about 4106670, 1029877, and 644092 by the year 2100 respectively. Under both RCP (Representative Concentration Pathway) 4.5 and RCP8.5 scenarios, the reservoir inflow indicates that the level of reservoirs at Foresthill, Diremogolo, Gabane hill, Oodi hill and Mabutswe will be reduced during 2080-2098 period

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